1. Field of the Invention
The disclosures herein generally relate to a lubricant supplying device, an image forming apparatus and a process cartridge.
2. Description of the Related Art
It is known that there are image forming apparatuses such as printers, facsimile machines, copying machines, etc., provided with a lubricant supplying device to supply lubricant to a surface of a photoreceptor or an image bearing body, such as an intermediate transfer belt, to protect the image bearing member or to reduce friction.
The lubricant supplying device provides a supplying member making contact with a bar-shaped solid lubricant to be rubbed and scraped off by the supplying member, for generating fine-powder lubricant to be supplied to the image bearing member. The lubricant supplying device also provides a lubricant holding member at the opposing end to the contacting end with the supplying member. The lubricant holding member is held in a case of the lubricant supplying device, and movable in a direction moving toward/away from the solid lubricant. Also, in the opposing space in the case to the side holding the solid lubricant of the lubricant holding member, a pressure applying mechanism is provided to apply pressure to the end of the lubricant holding member holding the solid lubricant toward the supplying member.
When the supplying member rotates, the supplying member rubs the solid lubricant contacting with it, scrapes off lubricant to be transferred to the supplying member, which is then applied to the surface of the image bearing member. While the solid lubricant is scraped off gradually by being rubbed by the supplying member, the lubricant holding member moves toward the supplying member. With this movement, the solid lubricant makes contact with the supplying member from the beginning to the end of its usage so that the supplying member can scrape off the solid lubricant well.
If an image forming operation is executed after the lubricant has been completely consumed, the image bearing member wears out due to deterioration because the image bearing member is not protected with the lubricant. Japanese Laid-open Patent Application No. 2010-271665 (referred to as Patent document 1, hereafter), and Japanese Laid-open Patent Application No. 2011-197126 (referred to as Patent document 2, hereafter) disclose a lubricant supplying device providing a remaining amount detecting section to indicate when the remaining amount of a solid lubricant becomes only a small amount, which is detected by the length of the solid lubricant in the moving direction (called the height of the solid lubricant, hereafter) becomes less than a prescribed value when being scraped off.
In the lubricant supplying device described in Patent documents 1 and 2, the lubricant holding member is configured with a conductive member with which an electrode member comes into contact. The remaining amount detecting section described in Patent document 1 or the sixth modified example in Patent document 2 is in a conductive state in which the conductive member and the lubricant holding member contact each other at the beginning of the usage of the lubricant. When the height of the solid lubricant is reduced and the remaining amount of the solid lubricant becomes only a small amount, the conductive member and the lubricant holding member are separated to be in a non-conductive state. The transition from the conductive state to the non-conductive state makes it possible to detect when the remaining amount of the solid lubricant becomes only a small amount.
In the remaining amount detecting section described in the fifth modified example in Patent document 2, on the contrary to the above, at the beginning of the usage of the lubricant, the conductive member and the lubricant holding member are separated to be in a non-conductive state. When the height of the solid lubricant is reduced to less than a prescribed value, the conductive member and the lubricant holding member come into contact with each other to be in a conductive state. The transition from the non-conductive state to the conductive state makes it possible to detect when the remaining amount of the solid lubricant becomes only a small amount.
However, in the remaining amount detecting section described in Patent document 1 or 2 which monitors whether the height of the solid lubricant is reduced to less than a prescribed value to detect whether the remaining amount of the solid lubricant becomes only a small amount, there is a problem of a false detection of the remaining amount of the lubricant. The inventors of the present invention have researched this issue intensively to identify the cause of the false detection. It turns out that the false detection may happen if the detection of the remaining amount is executed while the lubricant is being supplied to a target object of lubrication. The reason is as follows. While the lubricant is being supplied to a target object of lubrication, the solid lubricant is vibrating in the height direction of the solid lubricant because the supplying member rubs the solid lubricant. The vibration makes the position of the lubricant holding member fluctuate in the height direction of the solid lubricant. As a result, the contact between the lubricant holding member and the electrode member becomes unstable to cause a false detection in which the transition to a conductive state does not happen even if the remaining amount of the lubricant becomes less than the prescribed value, which is falsely recognized that the remaining amount of the lubricant being more than the prescribed value; or another false detection in which a conductive state remains unchanged even if the remaining amount of the lubricant becomes less than the prescribed value, which is falsely recognized as the remaining amount of the lubricant being more than the prescribed value.
As above, the problem of the false detection is described with the remaining amount detecting section to detect electrical continuity between the electrode member and the lubricant holding member. A similar problem may occur with other types of remaining amount detecting sections. For example, in the lubricant applying device providing a remaining amount detecting section to indicate when the remaining amount of the lubricant becomes near-end by pushing a switch, a similar problem may occur.